The effects of addition of Al and equivalent atomic ratio of Ag and Al on the glass-forming ability (GFA) of the Cu50Zr50 alloy are investigated. It is found that the alloy with the highest GFA is the Cu46Zr46Al8 alloy in ternary (Cu50Zr50)100−xAlx alloys, and the critical diameter is at least 8 mm. The simultaneous addition of Ag and Al is more effective to increase the glass-forming ability of the binary Cu50Zr50 alloy. The critical diameter of a glassy rod is 12 mm for the Cu42Zr42Al8Ag8 alloy. High stabilization of the supercooled liquid is the reason for high GFA of the Cu46Zr46Al8 and Cu42Zr42Al8Ag8 alloys. Both glassy alloys exhibited high fracture strength above 1960 MPa, but no distinct plastic strain is seen. There is no evident difference in the mechanical properties of the as-cast Cu42Zr42Al8Ag8 glassy rods with different diameters.